1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory device having a multi-layer structure in which cross-point memory cells are laminated and a producing method thereof.
2. Description of the Related Art
Conventionally, a flash memory is well known as an electrically-rewritable nonvolatile memory. In the flash memory, NAND connection or NOR connection of memory cells having floating gate structures is established to form a memory cell array. A ferroelectric memory is also well known as a nonvolatile, high-speed random access memory.
On the other hand, a resistance change type memory in which a variable resistive element is used in the memory cell is proposed as a technique of further achieving a finer design rule of the memory cell. Examples of the variable resistive element include a phase-change memory element in which a resistance value is changed according to a state change between crystalline state and an amorphous state of a chalcogenide compound, an MRAM element in which a resistance change of a tunnel magnetoresistive effect is used, a memory element of a polymer ferroelectric RAM (PFRAM) in which the resistive element is made of a conductive polymer, and an ReRAM element in which the resistance change is generated by electric pulse application (for example, see Japanese Patent Application Laid-Open No. 2006-344349, paragraph [0021]).
In the resistance change type memory, because the memory cell can be formed by a series circuit of a Schottky diode and a resistance change element instead of a transistor, advantageously a three-dimensional structure is formed by ease lamination to achieve the further integration (for example, see Japanese Patent Application Laid-Open No. 2005-522045).
However, even if the resistance change type memory is used, there is a limitation to L/S (Line/Space) of about 40 nm of the memory cell array in a current lithography technique. Therefore, there is a demand for the finer design rule of the memory cell.